Method and apparatus for providing a magnetic read sensor having a thin pinning layer and improved magnetoreistive coefficient

ABSTRACT

A method and apparatus for providing a magnetic read sensor having a thin pinning layer and improved magnetoresistive coefficient ΔR/R is disclosed. A thin IrMn alloy pinning layer is disposed adjacent a composite pinned layer, wherein the percentage of iron in the pinned layer adjacent the thin IrMn alloy pinning layer in the range of 20-40% to provide maximum pinning.

RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.10/837,280, filed Apr. 30, 2004, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to magnetic read sensors, and moreparticularly to a method and apparatus for providing a magnetic readsensor having a thin pinning layer and improved magnetoresistivecoefficient ΔR/R.

2. Description of Related Art

The heart of a computer is typically a magnetic disk drive whichincludes a rotating magnetic disk, a slider that has write and readheads, a suspension arm above the rotating disk and an actuator arm. Thesuspension arm biases the slider into contact with a parking ramp or thesurface of the disk when the disk is not rotating but, when the diskrotates, air is swirled by the rotating disk adjacent an air bearingsurface (ABS) of the slider causing the slider to ride on an air bearinga slight distance from the surface of the rotating disk. When the sliderrides on the air bearing the actuator arm swings the suspension arm toplace the write and read heads over selected circular tracks on therotating disk where field signals are written and read by the write andread heads. The write and read heads are connected to processingcircuitry that operates according to a computer program to implement thewriting and reading functions.

Conventional magnetoresistive (MR) sensors, such as those used inmagnetic recording disk drives, operate on the basis of the anisotropicmagnetoresistive (AMR) effect in which a component of the read elementresistance varies as the square of the cosine of the angle between themagnetization in the read element and the direction of sense currentflow through the read element. Recorded data can be read from a magneticmedium because the external magnetic field from the recorded magneticmedium (the signal field) causes a change in the direction ofmagnetization in the read element, which in turn causes a change inresistance in the read element and a corresponding change in the sensedcurrent or voltage.

A different and more pronounced magnetoresistance, called giantmagnetoresistance (GMR), has been observed in a variety of magneticmultilayered structures, the essential feature being at least twoferromagnetic metal layers separated by a non-ferromagnetic metal layer.The physical origin of the GMR effect is that the application of anexternal magnetic field causes a variation in the relative orientationof neighboring ferromagnetic layers. This in turn causes a change in thespin-dependent scattering of conduction electrons and thus theelectrical resistance of the structure. The resistance of the structurethus changes as the relative alignment of the magnetizations of theferromagnetic layers changes.

A particularly useful application of GMR is a sandwich structure, calleda spin valve, comprising two uncoupled ferromagnetic layers separated bya nonmagnetic metal layer in which the magnetization of one of theferromagnetic layers is pinned. The pinning may be achieved bydepositing the layer onto an antiferromagnetic layer, whichexchange-couples to the pinned layer. The unpinned layer or freeferromagnetic layer is free to rotate in the presence of any smallexternal magnetic field.

Spin valve structures have been identified in which the resistancebetween two uncoupled ferromagnetic layers is observed to vary as cosineof the angle between the magnetizations of the two layers and isindependent of the direction of current flow. The spin valve produces amagnetoresistance that, for selected combinations of materials, isgreater in magnitude than AMR. In general, the larger ΔR/R is the betterthe spin valve's performance.

Spin valve (GMR) read heads require two main improvements for futurehigh density recording needs, which are larger signal for detecting eversmaller magnetic bits and smaller read gaps requiring thinner pinninglayers. Most previously described spin valve use antiferromagnetic orpinning layer deposited adjacent to the pinned layer for exchangecoupling to fix or pin the magnetization of the pinned layer. Throughexchange anisotropy with the antiferromagnetic layer, the magnetizationof the pinned layer is held rigid against small field excitations, suchas those that occur from the signal field to be sensed.

In the presence of some magnetic fields the magnetic moment of thepinned layer can be rotated antiparallel to the pinned direction. Thequestion then is whether the magnetic moment of the pinned layer willreturn to the pinned direction when the magnetic field is relaxed. Thisdepends upon the strength of the exchange coupling field and thecoercivity of the pinned layer. If the coercivity of the pinned layerexceeds the exchange coupling field between the pinning and pinnedlayers the exchange coupling field will not be strong enough to bringthe magnetic moment of the pinned layer back to the original pinneddirection. Until the magnetic spins of the pinning layer are reset, theread head is rendered inoperative. Accordingly, there is a strong feltneed to increase the exchange coupling field between the pinning layerand the pinned layer so that the spin valve sensor has improved thermalstability.

Another parameter that indicates the performance of the pinning of thepinned layer is the pinning field H_(p) between the pinning and pinnedlayers. The pinning field, which is somewhat dependent upon the exchangecoupling field H_(ex), is the applied field at which the magnetic momentof the pinned layer commences to rotate in a substantial manner. If thepinning field H_(p) is low, the orientation of the pinned layer will notbe controlled thereby degrading performance of the read head.Accordingly, it is desirable to maximize the pinning field H_(p).

The thickest layer in a spin valve sensor is typically the pinninglayer. An exceptionally thin pinning layer, which is capable of pinningthe pinned layer, is iridium manganese (IrMn). While this pinning layeris highly desirable from the standpoint of reducing the read gap betweenthe first and second shield layers, the magnetoresistive coefficientΔR/R of the sensor has been relatively low when the iridium manganese(IrMn) pinning layer is formed. It should be noted that when themagnetoresistive coefficient ΔR/R is increased that the linear bitdensity is still further increased because the read head has an improvedread signal and can read more bits per linear inch along the track.

It can be seen then that there is a need for a method and apparatus forproviding a magnetic read sensor having a thin pinning layer andimproved magnetoresistive coefficient ΔR/R.

SUMMARY OF THE INVENTION

To overcome the limitations described above, and to overcome otherlimitations that will become apparent upon reading and understanding thepresent specification, the present invention discloses a method andapparatus for providing a magnetic read sensor having a thin pinninglayer and improved magnetoresistive coefficient ΔR/R.

The present invention solves the above-described problems by providing athin IrMn alloy pinning layer adjacent a composite pinned layer, whereinthe percentage of iron in the pinned layer adjacent the thin IrMn alloypinning layer in the range of 20-40% to provide maximum pinning.

A magnetic read head in accordance with the principles of the presentinvention includes a ferromagnetic pinned layer structure comprising atleast two pinned layers, the ferromagnetic pinned structure having ahigh positive magnetostriction, a iridium manganese (IrMn) alloy pinninglayer, exchange coupled to the pinned layer structure, for pinning themagnetic moment of the pinned layer structure, a free layer structurehaving a first magnetization that is free to rotate and a spacer layerdisposed between the free layer structure and the ferromagnetic pinnedlayer structure, wherein the at least two pinned layers of theferromagnetic pinned layer structure provide maximum exchange couplingbetween the pinned layer structure and the iridium manganese alloypinning layer and wherein thickness of at least two of the pinned layersare equal.

In another embodiment of the present invention, a magnetic storagedevice is provided. The magnetic storage device includes a magneticmedia for storing data thereon, a motor, coupled to the magnetic media,for translating the magnetic media, a transducer for reading and writingdata on the magnetic media and an actuator, coupled to the transducer,for moving the transducer relative to the magnetic media, wherein thetransducer includes a read sensor having a ferromagnetic pinned layerstructure comprising at least two pinned layers, the ferromagneticpinned structure having a high positive magnetostriction, a iridiummanganese (IrMn) alloy pinning layer, exchange coupled to the pinnedlayer structure, for pinning the magnetic moment of the pinned layerstructure, a free layer structure having a first magnetization that isfree to rotate and a spacer layer disposed between the free layerstructure and the ferromagnetic pinned layer structure, wherein the atleast two pinned layers of the ferromagnetic pinned layer structureprovide maximum exchange coupling between the pinned layer structure andthe iridium manganese alloy pinning layer and wherein thickness of atleast two of the pinned layers are equal.

In another embodiment of the present invention, a method for providing amagnetic read sensor having a thin pinning layer and improvedmagnetoresistive coefficient is provided. The method includes forming aferromagnetic pinned layer structure comprising at least two pinnedlayers, the ferromagnetic pinned structure having a high positivemagnetostriction, forming a iridium manganese (IrMn) alloy pinninglayer, exchange coupled to the pinned layer structure, for pinning themagnetic moment of the pinned layer structure, forming a free layerstructure having a first magnetization that is free to rotate andforming a spacer layer disposed between the free layer structure and theferromagnetic pinned layer structure, wherein the at least two pinnedlayers of the ferromagnetic pinned layer structure provide maximumexchange coupling between the pinned layer structure and the iridiummanganese alloy pinning layer and wherein thickness of at least two ofthe pinned layers are equal.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and form a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to accompanying descriptive matter, in whichthere are illustrated and described specific examples of an apparatus inaccordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates a storage system according to an embodiment of thepresent invention;

FIG. 2 illustrates one storage system according to an embodiment of thepresent invention;

FIG. 3 illustrates a slider mounted on a suspension according to anembodiment of the present invention;

FIG. 4 illustrates an ABS view of the slider and the magnetic headaccording to an embodiment of the present invention;

FIG. 5 is a side cross-sectional elevation view of a magnetic head;

FIG. 6 is an air bearing surface (ABS) view of the magnetic head of FIG.5;

FIG. 7 illustrates the connect leads coupled to the coil for the writepole piece;

FIG. 8 illustrates the basic components of a typical current-in-plane(CIP) GMR sensor according to one embodiment of the present invention;

FIG. 9 shows a current-perpendicular-to-plane (CPP) sensor according toone embodiment of the present invention;

FIG. 10 illustrates a dual spin valve magnetoresistive structure havingthin pinning layers and improved magnetoresistive coefficient ΔR/Raccording to an embodiment of the present invention;

FIG. 11 illustrates a single magnetoresistive structure having a thinpinning layer and improved magnetoresistive coefficient ΔR/R accordingto an embodiment of the present invention;

FIG. 12 illustrates another single magnetoresistive structure having athin pinning layer and improved magnetoresistive coefficient ΔR/Raccording to an embodiment of the present invention;

FIG. 13 illustrates a Tunnel MR sensor that uses IrMnCr as theantiferromagnetic material to provide a zero net moment pinned layer anda thin Ru layer according to another embodiment of the presentinvention;

FIG. 14 illustrates a second Tunnel MR sensor that includes a softmagnetic layer for improving the magnetic properties of the free layeraccording to another embodiment of the present invention;

FIG. 15 illustrates a CPP GMR sensor that uses an IrMnCr pinning layerto provide a zero net moment in the pinned layer and a thin Ru layeraccording to another embodiment of the present invention; and

FIG. 16 is a flow chart of the method for providing a magnetic readsensor having a thin pinning layer and improved magnetoresistivecoefficient ΔR/R.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the embodiments, reference is made tothe accompanying drawings that form a part hereof, and in which is shownby way of illustration the specific embodiments in which the inventionmay be practiced. It is to be understood that other embodiments may beutilized because structural changes may be made without departing fromthe scope of the present invention.

The present invention provides a method and apparatus for providing amagnetic read sensor having a thin pinning layer and improvedmagnetoresistive coefficient ΔR/R.

The present invention provides a thin IrMn alloy pinning layer adjacenta composite pinned layer, wherein the percentage of iron in the pinnedlayer adjacent the thin IrMn alloy pinning layer in the range of 20-40%to provide maximum pinning. It also may be desirable for the thicknessesof the outer ferromagnetic layers to be comparable.

FIG. 1 illustrates an exemplary storage system 100 according to thepresent invention. A transducer 110 is under control of an actuator 120,whereby the actuator 120 controls the position of the transducer 110.The transducer 110 writes and reads data on magnetic media 130. Theread/write signals are passed to a data channel 140. A signal processor150 controls the actuator 120 and processes the signals of the datachannel 140 for data exchange with external Input/Output (I/O) 170. I/O170 may provide, for example, data and control conduits for a desktopcomputing application, which utilizes storage system 100. In addition, amedia translator 160 is controlled by the signal processor 150 to causethe magnetic media 130 to move relative to the transducer 110. Thepresent invention is not meant to be limited to a particular type ofstorage system 100 or to the type of media 130 used in the storagesystem 100.

FIG. 2 illustrates one particular embodiment of a multiple magnetic diskstorage system 200 according to the present invention. In FIG. 2, a harddisk drive storage system 200 is shown. The system 200 includes aspindle 210 that supports and rotates multiple magnetic disks 220. Thespindle 210 is rotated by motor 280 that is controlled by motorcontroller 230. A combined read and write magnetic head 270 is mountedon slider 240 that is supported by suspension 250 and actuator arm 240.Processing circuitry exchanges signals that represent information withread/write magnetic head 270, provides motor drive signals for rotatingthe magnetic disks 220, and provides control signals for moving theslider 260 to various tracks. Although a multiple magnetic disk storagesystem is illustrated, a single magnetic disk storage system is equallyviable in accordance with the present invention.

The suspension 250 and actuator arm 240 position the slider 260 so thatread/write magnetic head 270 is in a transducing relationship with asurface of magnetic disk 220. When the magnetic disk 220 is rotated bymotor 280, the slider 240 is supported on a thin cushion of air (airbearing) between the surface of disk 220 and the ABS 290. Read/writemagnetic head 270 may then be employed for writing information tomultiple circular tracks on the surface of magnetic disk 220, as well asfor reading information therefrom.

FIG. 3 illustrates a sensor assembly 300. In FIG. 3, a slider 320 ismounted on a suspension 322. First and second solder connections 302 and308 connect leads from the sensor 318 to leads 310 and 314,respectively, on suspension 322 and third and fourth solder connections304 and 306 connect to the write coil (not shown) to leads 312 and 316,respectively, on suspension 322.

FIG. 4 is an ABS view of slider 400 and magnetic head 410. The sliderhas a center rail 420 that supports the magnetic head 410, and siderails 430 and 460. The support rails 420, 430 and 460 extend from across rail 440. With respect to rotation of a magnetic disk, the crossrail 440 is at a leading edge 450 of slider 400 and the magnetic head410 is at a trailing edge 470 of slider 400.

The above description of a typical magnetic recording disk drive system,shown in the accompanying FIGS. 1-4, is for presentation purposes only.Storage systems may contain a large number of recording media andactuators, and each actuator may support a number of sliders. Inaddition, instead of an air-bearing slider, the head carrier may be onethat maintains the head in contact or near contact with the disk, suchas in liquid bearing and other contact and near-contact recording diskdrives.

FIG. 5 is a side cross-sectional elevation view of a magnetic head 540.The magnetic head 540 includes a write head portion 570 and a read headportion 572. The read head portion 572 includes a sensor 574. FIG. 6 isan ABS view of the magnetic head of FIG. 5. The sensor 574 is sandwichedbetween first and second gap layers 576 and 578, and the gap layers aresandwiched between first and second shield layers 580 and 582. In apiggyback head as shown in FIG. 5, the second shield layer (S2) 582 andthe first pole piece (PI) 592 are separate layers. The first and secondshield layers 580 and 582 protect the MR sensor element 574 fromadjacent magnetic fields. More conventionally, the second shield 582also functions as the first pole (PI) 592 of the write element, givingrise to the term “merged MR head.” However, the present invention is notmeant to be limited to a particular type of MR head.

In response to external magnetic fields, the resistance of the sensor574 changes. A sense current is conducted through the sensor causesthese resistance changes to be manifested as voltage changes. Thesevoltage changes are then processed as readback signals by the signalprocessing system 350 shown in FIG. 3.

The write head portion of the magnetic head includes a coil layer 584sandwiched between first and second insulation layers 586 and 588. Athird insulation layer 590 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 584. The first, second and third insulation layers are referred toin the art as an “insulation stack.” The coil layer 584 and the first,second and third insulation layers 586, 588 and 590 are sandwichedbetween first and second pole piece layers 592 and 594. The first andsecond pole piece layers 592 and 594 are magnetically coupled at a backgap 596 and have first and second pole tips 598 and 501 which areseparated by a write gap layer 502 at the ABS. The first pole piecelayer 592 is separated from the second shield layer 582 by an insulationlayer 503.

FIG. 7 illustrates a view of the connect leads 520, 522 coupled to thecoil 584 for the write pole piece 594. As shown in FIGS. 4-7, first andsecond solder connections 404 and 406 connect leads from the sensor 574to leads 412 and 414 on the suspension 444, and third and fourth solderconnections 416 and 418 connect leads 520 and 522 from the coil 584 (seeFIG. 7) to leads 424 and 426 on the suspension.

FIG. 8 illustrates the basic components of a typical current-in-plane(CIP) GMR sensor 800 according to one embodiment of the presentinvention. The sensor 800 includes a ferromagnetic reference layer 806with a fixed transverse magnetic moment (pointing into the page) and aferromagnetic free layer 810 with a rotatable magnetization vector,which can rotate about the longitudinal direction in response totransverse magnetic signal fields. The direction of the magnetic momentof the reference layer 806 is typically fixed by exchange coupling withan antiferromagnetic layer 804. Exchange-pinned reference layer 806 andfree layer 810 are separated by a thin electrically conductivenonmagnetic layer 808. Hard bias layers 812 provide a longitudinalbiasing magnetic field to stabilize the magnetization of the free layer810 approximately in a longitudinal orientation in the absence of otherexternal magnetic fields. Sensor 800 further includes top electricalleads 814 in proximity with hard bias layers 812, and a layer 802adjacent to the antiferromagnetic layer 804, which represents acombination of the substrate, undercoat, and seed layers. For a shieldedsensor, layer 802 may additionally include the bottom shield andinsulation layers (for CIP sensors) or electrical contact layers (forCPP sensors).

FIG. 9 shows a current-perpendicular-to-plane (CPP) sensor 900 accordingto one embodiment of the present invention. CPP sensor 900 includes aferromagnetic reference layer 906 with a fixed magnetic moment orientedtransversely (into the page) and a ferromagnetic free layer 910 with arotatable magnetization vector, which can rotate about the longitudinaldirection in response to transverse magnetic signal fields. Thedirection of the magnetic moment of the reference layer 906 is typicallyfixed by exchange coupling with an antiferromagnetic layer 904. Theexchange-pinned reference layer 906 and free layer 910 are spaced apartby a non-magnetic layer 908. For MTJ devices, layer 908 includes anelectrically insulating tunnel barrier layer. For CPP-GMR devices, layer908 is electrically conductive, and is analogous to layer 808 of theCIP-GMR sensor of FIG. 8. Hard bias layers 912 are electricallyinsulated from the sensor stack and the top electrical lead 916 byinsulating layers 914 and 918 respectively. Hard bias layers 912 providea longitudinal biasing magnetic field to stabilize the magnetization ofthe free layer 910. Sensor 900 further includes a layer 902, which issimilar to layer 802 of sensor 800, in proximity with theantiferromagnetic layer 904.

The above description of a CPP and CIP magnetic sensor, shown in theaccompanying FIGS. 8-9, is for presentation purposes only. Those skilledin the art will recognize that other embodiments that provide CPP andCIP sensors are possible, including dual sensor structures, self-pinnedstructures, etc.

FIG. 10 illustrates a dual spin valve magnetoresistive structure 1000having thin pinning layers and improved magnetoresistive coefficientΔR/R according to an embodiment of the present invention. In FIG. 10, aseed layer of Ta 1004 and NiFe 1006 are deposited on a first shield1002. Alternatively, a NiFeCr layer may be used to provide anon-magnetic material for forming the first thin pinning layer on. Afirst thin pinning layer of iridium manganese chromium (IrMnCr) 1010 isformed over the NiFe layer 1006. A first pinned layer 1020 is formedover the first IrMnCr pinning layer 1010. The first pinned layer 1020includes a first CoFe layer 1022, an interlayer 1024, such as ruthenium,and a second CoFe layer 1026. A first spacer 1030, e.g., copper, isformed over the first pinned layer 1020. A free layer 1040 is formedover the first spacer 1030. The free layer 1040 includes a third CoFelayer 1042, a NiFe layer 1034 and a fourth CoFe layer 1046. A secondspacer 1050, e.g., copper, is formed over the free layer 1040. A secondpinned layer 1060 is formed over the second spacer 1050. The secondpinned layer 1060 includes a fifth CoFe layer 1062, an interlayer 1064,such as ruthenium, and a sixth CoFe layer 1066. A second thin pinninglayer of iridium manganese chromium (IrMnCr) 1070 is formed over thesecond pinned layer 1060. A cap 1080 is formed over the second thinpinning layer 1070. A second shield 1090 is formed over the cap 1080.

In FIG. 10, the layers 1022, 1066 of the pinned layers 1020, 1060adjacent the pinning layers 1010, 1070 respectively may be cobalt iron(CoFe), which has a high magnetostriction so that after lapping the headthe pinned layers 1020, 1060 have a stress-induced anisotropyperpendicular to the ABS which supports the exchange coupling betweenthe pinning layers 1010, 1070 and the first layers 1022, 1066 of thepinned layers 1020, 1060. Also, the antiferromagnetic exchange couplingis inversely proportional to the net pinning moment. Thus, the first1022 and second 1026 CoFe layers and the fifth 1062 and sixth 1066 CoFelayers should have approximately the same thickness to provide a low netpinning moment, which increases exchange coupling between the firstferromagnetic films 1022, 1066 of the pinned layers 1020, 1060 and thepinning layers 1010, 1070. Moreover, the CoFe layers 1022, 10066 next tothe pinning layers 1010, 1070 may include a percentage of iron thatprovides maximum exchange coupling. The high exchange coupling promoteshigher thermal stability of the head. Also, the addition of chromiummakes the pinning layers 1010, 1070 more corrosion resistant thereforeresulting in improved reliability of the GMR signal.

To provide higher magnetostriction and exchange coupling, the thicknessof the IrMnCr layers 1010, 1070 should be in the range of 30-90 Å. Underpinning, as the magnetostriction anisotropy field, H_(k), becomes small,unidirectional bias from the pinning layers 1010, 1070 prevents theamplitude from flipping.

FIG. 11 illustrates a single magnetoresistive structure 1100 having athin pinning layer and improved magnetoresistive coefficient ΔR/Raccording to another embodiment of the present invention. In FIG. 10, aseed layer of Ta 1104 and NiFeCr 1106 is formed. The NiFeCr 1106provides a non-magnetic material for forming the thin pinning layer 1110on. The thin pinning layer of iridium manganese (IrMn) 1110 is formedover the NiFeCr layer 1106. A first pinned layer 1120 is formed over theIrMn pinning layer 1110. The first pinned layer 1120 includes a Co₇₀Fe₃₀layer 1122, an interlayer 1124, such as ruthenium, and a CoFe₁₀ layer1126. A spacer 1130, e.g., copper, is formed over the pinned layer 1120.A free layer 1140 is formed over the spacer 1130. The free layer 1140includes a second CoFe₁₀ layer 1142 and a NiFe layer 1144. A cap 1180 isformed over the free layer 1140. The cap 1180 may be a tantalum layer.

In FIG. 11, the percentage of iron in the first cobalt iron layer 1122of the pinned layer 1120 should be in the range of 20-40% to providemaximum pinning, wherein 30% iron is preferred and shown. An IrMnpinning layer 1110 of 30 Å provides sufficient exchange coupling withCo₇₀Fe₃₀ 1122 layer. However, those skilled in the art will recognizethat an IrMnCr pinning layer may be used and is generally preferred forthe pinning layer. The large anisotropy field, H_(k), of the IrMnpinning layer 1110 will provide pinning while exchange coupling from theIrMn 1120 will prevent the amplitude from flipping.

FIG. 12 illustrates another single magnetoresistive structure 1200having a thin pinning layer and improved magnetoresistive coefficientΔR/R according to another embodiment of the present invention. In FIG.12, a seed layer of silicon 1204 and copper 1206 is formed. A thinpinning layer of iridium manganese chromium (IrMnCr) 1210 is formed overthe copper seed layer 1206. A pinned layer 1220 is formed over theIrMnCr pinning layer 1210. The pinned layer 1220 includes a layer ofCo₇₀Fe₃₀ 1222, an interlayer 1224, such as ruthenium, and a CoFe₅₀ layer1226. A spacer 1230, e.g., copper, is formed over the pinned layer 1220.A free layer 1240 is formed over the spacer 1230. A cap 1280 is formedover the free layer 1240.

The copper seed layer 1206 allows current shunting, but the structureshown is acceptable for CPP sensors. Also, the percentage of iron in thesecond cobalt iron layer 1226 of the pinned layer 1220 is increased toapproximately 50%. Improved self-pinning is provided using the thinlayer of IrMnCr AFM 1210, which provides a restoring field to the sensoras the sensor magnetic orientation flips due to a decrease in theanisotropy pinning, H_(k), due to external stress. The first pinnedlayer of Co₇₀Fe₃₀ 1222 provides enhanced exchange coupling as well asstronger anisotropy field, H_(k).

While FIGS. 10-12 show both IrMn and IrMnCr used for the pinning layer,IrMnCr is preferred. Moreover, those skilled in the art will recognizethat the structures providing the effects described above with referenceto FIGS. 10-12 may be interchange. For example, the sensor 1200 shown inFIG. 12 may be configured with the layer of tantalum 1104 and NiFeCr1106 shown in FIG. 11; the first pinned layer of Co₇₀Fe₃₀ 1122 shown inFIG. 11 may be used in place of the first CoFe layer 1022 and/or thesixth CoFe layer 1066 of FIG. 10; etc. Other modifications may be madewithout departing from the scope of the present invention.

FIG. 13 illustrates a Tunnel MR sensor 1300 that uses IrMnCr as theantiferromagnetic material to provide a zero net moment pinned layer anda thin Ru layer according to another embodiment of the presentinvention. In FIG. 13, a thin pinning layer of iridium manganesechromium (IrMnCr) 1310 is formed over a tantalum layer 1302 andruthenium layer 1304. A pinned layer 1320 is formed over the IrMnCrpinning layer 1310. The pinned layer 1320 includes a layer of Co₇₅Fe₂₅1322, an interlayer 1324, such as ruthenium, and a CoFeB layer 1326. Atunnel barrier 1330 of magnesium oxide (MgO) is formed over the CoFeBlayer 1326. A free layer 1340 is formed over the tunnel barrier layer1330. The free layer 1330 includes a thin layer of CoFe 1342 and a toplayer of CoFeB 1344. Layers of ruthenium 1382, tantalum 1384 andruthenium 1386 are formed to provide a cap layer 1380 over the freelayer 1340.

Tunnel MR (TMR) sensors 1300 have a magnetic free layer 1340 and amagnetic pinned layer 1320 similar to a GMR or spin valve. The tunnelvalve 1300, however, has a thin electrically insulating barrier layer1330 sandwiched between the free 1340 and pinned 1320 layers rather thanan electrically conductive spacer layer. A large TMR coefficient isachieved using magnesium oxide (MgO) as the tunnel barrier 1330. TheCoFeB layer 1326 provides an amorphous layer for forming the MgO tunnelbarrier 1330 to provide the high GMR coefficient by allowing theinsulating MgO layer to be a highly oriented crystalline structure.

To pin the orientation of the ferromagnetic pinned layer 1320, thepinned layer 1320 is exposed to a high magnetic field. However,manufacturing of a tunnel junction MR sensor is typically difficultbecause of the need to apply the high magnetic fields to pin the pinnedlayers 1320. According to the embodiment of the present inventionillustrated in FIG. 13, the ruthenium interlayer 1324 is made thin,e.g., around 3.5 to 4.5 Å, to achieve stronger pinning between thepinned layers 1322, 1326. This increases manufacturing yield because thepinned layers 1322, 1326 are strongly pinned and, as a result do notdisorient during fabrication processes or during use in the hard diskdrive.

FIG. 14 illustrates a second Tunnel MR sensor 1400 that includes a softmagnetic layer for improving the magnetic properties of the free layeraccording to another embodiment of the present invention. Again, a thinpinning layer of iridium manganese chromium (IrMnCr) 1410 is used as theantiferromagnetic material to provide a zero net moment pinned layer. Apinned layer 1420 is formed over the IrMnCr pinning layer 1410. Thepinned layer 1420 includes a layer of Co₇₅Fe₂₅ 1422, an interlayer 1424,such as ruthenium, and a CoFeB layer 1426. A tunnel barrier 1430 ofmagnesium oxide (MgO) is formed over the CoFeB layer 1426. A free layer1440 is formed over the tunnel barrier layer 1430. The free layer 1430includes a thin layer of CoFe 1442 and a top layer of CoFeB 1444. Atantalum layer 1450 is formed over the layer of CoFeB 1444. A NiFe layer1452 is formed on the tantalum layer 1450. Layers of ruthenium 1482,tantalum 1484 and ruthenium 1486 are formed to provide a cap layer 1480.

The NiFe layer 1452 provides improved magnetic properties to the freelayer 1440 since the NiFe layer 1452 is soft magnetically therebyincreasing the sensitivity of the sensor. High sensitivity means arelatively large percentage change in electrical resistance per unitapplied magnetic field. However, forming the NiFe layer directly on theCoFeB layer or the CoFe layer results in a decrease in the TMRcoefficient. The TMR coefficient of the TMR sensor is expressed asΔR_(T)/R_(//), where R_(//) is a resistance measured when themagnetizations of the sense and reference layers are parallel to eachother, and ΔR_(T) is the difference in resistance between when thereference/free layer moments are parallel and when these areantiparallel.

A higher TMR coefficient leads to higher signal sensitivity. Thus, adecrease in the TMR coefficient is undesirable. To prevent a decrease inthe TMR coefficient, the tantalum layer 1450 is formed before formingthe NiFe layer 1452. The tantalum layer 1450 oxidizes easily therebyeffectively providing an amorphous layer for forming the NiFe layer 1452on. Accordingly, the addition of the tantalum layer 1450 and the NiFelayer 1452 as shown in FIG. 14 improves the magnetic properties of thefree layer 1440 without decreasing the TMR coefficient.

FIG. 15 illustrates a CPP GMR sensor 1500 that uses an IrMnCr pinninglayer to provide a zero net moment in the pinned layer and a thin Rulayer according to another embodiment of the present invention. In a CPPsensor as shown in FIG. 15, the sense current flows from the top of thesensor to the bottom of the sensor perpendicular to the plane of thelayers of material making up the sensor.

In FIG. 15, a thin pinning layer of iridium manganese chromium (IrMnCr)1510 is used as the antiferromagnetic material to provide a zero netmoment pinned layer. A pinned layer 1520 is formed over the IrMnCrpinning layer 1510. The pinned layer 1520 includes a first layer ofCo₇₅Fe₂₅ 1522, an interlayer 1524, such as ruthenium, and a second layerof Co₇₅Fe₂₅ 1526. A third layer 1528 is formed on the second layer ofCo₇₅Fe₂₅ 1526. The third layer 1528 uses a Co₂XY layer, where X is amaterial chosen from a group that includes manganese, iron and chromium,and Y is a material chosen from a group that includes silicon, germaniumand aluminum. In a CPP GMR sensor, a copper spacer layer 1530 isprovided on the third layer 1528. A synthetic antiparallel free layer1540 is formed on the spacer layer 1530. The synthetic antiparallel freelayer 1540 includes a first free layer 1542 having a first layer ofCo₂XY 1543 and a second layer of CoFe 1544. An interlayer 1545, e.g.,ruthenium, is formed on the CoFe layer 1544. A second free layer 1546,oriented 180° from the first free layer 1542, is formed on theinterlayer 1545. The second free layer 1546 includes a third free layer1547 of CoFe 1548 and a fourth layer of NiFe 1549. A cap layer 1580 isformed over the NiFe layer 1549.

High spin polarization of the ferromagnetic materials adjacent thenonmagnetic spacer layer 1530 is essential for high magnetoresistance.However, Co, Fe and Ni alloys have only relatively lowspin-polarization. In contrast, certain half-metallic ferromagneticHeusler alloys, e.g., Co₂XY as defined above, exhibit near 100% spinpolarization and thus are candidates for providing high spinpolarization of the ferromagnetic materials adjacent the nonmagneticspacer layer 1530 for high magnetoresistance.

FIG. 16 is a flow chart 1600 of the method for providing a magnetic readsensor having a thin pinning layer and improved magnetoresistivecoefficient ΔR/R. In FIG. 16, a non-conductive seed layer is formed1610. A thin IrMn alloy pinning layer is formed on the seed layer 1620.A composite pinned layer is formed over the thin IrMn alloy pinninglayer, wherein the percentage of iron in the pinned layer adjacent thethin IrMn alloy pinning layer in the range of 20-40% to provide maximumpinning 1630.

While the write portions of the magnetic sensors illustrated herein havebeen shown as longitudinal magnetic recording write heads, the goal ofproviding higher areal densities for increased storage capacity requiresthe bit sizes to be decreased thereby leading to the transition toperpendicular write heads. Longitudinal magnetic recording involvesaligning each data bit horizontally in relation to the drive's spinningplatter. In perpendicular recording, each bit is aligned vertically—orperpendicularly—in relation to the disk drive's platter. Since the bitsdo not directly oppose each other, the need for transition packing issignificantly reduced. This allows bits to be more closely packed withsharper transition signals, facilitating easier bit detection and errorcorrection. The potential for higher areal density results. Accordingly,a person skilled in the art will readily recognize the embodiments ofthe present invention are applicable to either longitudinal recordingheads or perpendicular recording heads.

The foregoing description of the exemplary embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not with this detailed description, but rather bythe claims appended hereto.

1. A magnetic read head, comprising: a ferromagnetic pinned layerstructure comprising at least two pinned layers, the ferromagneticpinned structure having a high positive magnetostriction; an iridiummanganese (IrMn) alloy pinning layer, exchange coupled to the pinnedlayer structure, for pinning the magnetic moment of the pinned layerstructure; a free layer structure having a first magnetization that isfree to rotate; and a spacer layer disposed between the free layerstructure and the ferromagnetic pinned layer structure; wherein the atleast two pinned layers of the ferromagnetic pinned layer structureprovide maximum exchange coupling between the pinned layer structure andthe iridium manganese alloy pinning layer and wherein thickness of atleast two of the pinned layers are equal.
 2. The magnetic read head ofclaim 1, wherein the spacer layer is a manganese oxide layer.
 3. Themagnetic read head of claim 1, wherein the pinned layer comprises acobalt iron layer, an interlayer and a cobalt iron boron layer, whereinthe cobalt iron layer is formed on the pinning layer.
 4. The magneticread head of claim 1, wherein the free layer structure comprises acobalt iron layer and a cobalt iron boron layer, wherein the cobalt ironlayer is formed on the spacer layer.
 5. The magnetic read head of claim4 further comprising a tantalum layer formed on the cobalt iron boronlayer and a nickel iron layer formed on the tantalum layer.
 6. Themagnetic read head of claim 1, wherein the spacer layer furthercomprising a copper spacer layer for providing a conductive spacer layerbetween the free layer and the pinned layer.
 7. The magnetic read headof claim 6, wherein the pinned layer further comprises a third layer,the third layer comprising a Co₂XY layer, where X is a material chosenfrom a group that includes manganese, iron and chromium, and Y is amaterial chosen from a group that includes silicon, germanium andaluminum.
 8. The magnetic read head of claim 7, wherein the free layerstructure comprises a synthetic free layer comprising a first and secondfree layer separated by an interlayer, the first and second free layerhaving antiparallel magnetic orientations.
 9. The magnetic read head ofclaim 8, wherein the first free layer comprises a layer comprising acobalt iron free layer and a Co₂XY layer formed on the copper spacerlayer between the cobalt iron free layer and the copper spacer layer,where X is a material chosen from a group that includes manganese, ironand chromium, and Y is a material chosen from a group that includessilicon, germanium and aluminum.
 10. The magnetic read head of claim 8,wherein the second free layer comprises a cobalt iron free layer formedon the interlayer and a nickel iron layer formed on the cobalt iron freelayer.
 11. A magnetic storage device, comprising: a magnetic media forstoring data thereon; a motor, coupled to the magnetic media, fortranslating the magnetic media; a transducer for reading and writingdata on the magnetic media; and an actuator, coupled to the transducer,for moving the transducer relative to the magnetic media; wherein thetransducer includes a read sensor comprising: a ferromagnetic pinnedlayer structure comprising at least two pinned layers, the ferromagneticpinned structure having a high positive magnetostriction; an iridiummanganese (IrMn) alloy pinning layer, exchange coupled to the pinnedlayer structure, for pinning the magnetic moment of the pinned layerstructure; a free layer structure having a first magnetization that isfree to rotate; and a spacer layer disposed between the free layerstructure and the ferromagnetic pinned layer structure; wherein the atleast two pinned layers of the ferromagnetic pinned layer structureprovide maximum exchange coupling between the pinned layer structure andthe iridium manganese alloy pinning layer and wherein thickness of atleast two of the pinned layers are equal.
 12. The magnetic read head ofclaim 11, wherein the spacer layer is a manganese oxide layer.
 13. Themagnetic read head of claim 11, wherein the pinned layer comprises acobalt iron layer, an interlayer and a cobalt iron boron layer, whereinthe cobalt iron layer is formed on the pinning layer and wherein thefree layer structure comprises a cobalt iron layer and a cobalt ironboron layer, wherein the cobalt iron layer is formed on the spacerlayer.
 14. The magnetic read head of claim 13 further comprising atantalum layer formed on the cobalt iron boron layer and a nickel ironlayer formed on the tantalum layer.
 15. The magnetic read head of claim11, wherein the spacer layer further comprising a copper spacer layerfor providing a conductive spacer layer between the free layer and thepinned layer.
 16. The magnetic read head of claim 15, wherein the pinnedlayer further comprises a third layer, the third layer comprising aCo₂XY layer, where X is a material chosen from a group that includesmanganese, iron and chromium, and Y is a material chosen from a groupthat includes silicon, germanium and aluminum.
 17. The magnetic readhead of claim 16, wherein the free layer structure comprises a syntheticfree layer comprising a first and second free layer separated by aninterlayer, the first and second free layer having antiparallel magneticorientations.
 18. The magnetic read head of claim 17, wherein the firstfree layer comprises a layer comprising a cobalt iron free layer and aCo₂XY layer formed on the copper spacer layer between the cobalt ironfree layer and the copper spacer layer, where X is a material chosenfrom a group that includes manganese, iron and chromium, and Y is amaterial chosen from a group that includes silicon, germanium andaluminum.
 19. The magnetic read head of claim 17, wherein the secondfree layer comprises a cobalt iron free layer formed on the interlayerand a nickel iron layer formed on the cobalt iron free layer.
 20. Amethod for providing a magnetic read sensor having a thin pinning layerand improved magnetoresistive coefficient, comprising: forming aferromagnetic pinned layer structure comprising at least two pinnedlayers, the ferromagnetic pinned structure having a high positivemagnetostriction; forming an iridium manganese (IrMn) alloy pinninglayer, exchange coupled to the pinned layer structure, for pinning themagnetic moment of the pinned layer structure; forming a free layerstructure having a first magnetization that is free to rotate; andforming a spacer layer disposed between the free layer structure and theferromagnetic pinned layer structure; wherein the at least two pinnedlayers of the ferromagnetic pinned layer structure provide maximumexchange coupling between the pinned layer structure and the iridiummanganese alloy pinning layer and wherein thickness of at least two ofthe pinned layers are equal.